Tokkai Hei 11-339831 published by the Japanese Patent Office in 1999 discloses a method of generating a reformate gas for a fuel cell stack. That is to say, liquid fuel such as methane or gasoline is evaporated by a vaporizer and the gaseous fuel is processed in a reformer in order to generate a reformate gas having hydrogen as its principal constituent. The vaporizer is provided with a combustor acting as a heat source in order to evaporate the fuel. The combustor supplies heat required for fuel evaporation to the vaporizer by combustion of an anode effluent in the fuel cell stack.